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Homework Help: Atomic % and weight %

  1. Nov 11, 2011 #1
    1. The problem statement, all variables and given/known data
    Given: 5x10^21 Phosphorous atoms/m^3 in solid solution in silicon

    Find: atomic percent and weight percent of Phosphorous atoms

    3. The attempt at a solution
    I know how to solve for at. % and wt. % when given two values, I am not sure how to get the second value given the mixture is a "solid solution"

    Do i have enough information to solve this?

    Solid solution means that it is completely mixed, but how would that lead me to a density of silicon that I could used to solve for at.% and wt.%?
  2. jcsd
  3. Nov 11, 2011 #2


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    Gold Member

    phosphorous in silicon...

    this sounds like semiconductor doping to me
    without any other information given I would assume this is the case, therefore I would decide the density of silicon by its cell structure and lattice parameter
  4. Nov 11, 2011 #3


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    Staff: Mentor

    Or just take density from any reliable source listing densities of elements. Amount of P is low enough to not change the density substantially.
  5. Nov 11, 2011 #4
    My book has nothing to do with "Doping" and my class has not covered this. My book actually, does not even cover at. % or wt. %.

    So I could just look up the density of silicon in as a solid and calc from there? Temperature does not matter here? (assuming that it doesn't, since the problem does not say)
  6. Nov 12, 2011 #5


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    Staff: Mentor

    Temperature doesn't matter - much. Density of solids doesn't change significantly with temperature (doesn't mean it doesn't change at all).
  7. Nov 12, 2011 #6
    thanks guys, looks like i just made this problem a bit more difficult than it had to be. I am going to use a density in g/cm^3 and convert it to atoms/m^2 and calculate at.% and wt. % from there.
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